Foldable helmet

ABSTRACT

A foldable helmet according to the present invention is a foldable helmet having a plurality of helmet fragments connected to each other to be rotatable about a common shaft and having a cap shape when the plurality of helmet fragments are unfolded in a stepped fashion. Each of the plurality of helmet fragments includes a slide-type connection means for connecting the inner peripheral surface of one helmet fragment to the outer peripheral surface of another helmet fragment inwardly adjacent thereto, along the circumferential direction, such that the unfolding is easy and the shape thereof is stably maintained at the time of the unfolding. According to the present invention, the plurality of helmet fragments are easily unfolded and folded. Therefore, when not in use, a user can fold the helmet fragments in a sliding fashion so that the size of the foldable helmet can be significantly reduced, thereby making the foldable helmet easy to carry and store. Further, while using the foldable helmet, a user wears the complete helmet formed by unfolding the helmet fragments, thereby sufficiently protecting the head of the user in a dangerous environment. According to the present invention, the plurality of helmet fragments can be easily unfolded and folded to allow a user to fold the helmet fragments in a sliding fashion, thereby significantly reducing the size of the foldable helmet, when the helmet is not in use. Therefore, the foldable helmet is easy to carry and store. Further, when using the foldable helmet, a user can sufficiently protect the head of the user even in a dangerous environment by wearing the complete helmet formed by unfolding the helmet fragments.

TECHNICAL FIELD

The present invention relates to a foldable helmet, and in particular to a foldable helmet wherein when not in use, it can be folded up and be carried or stored, and when in use, it can be unfolded and used in the form of a complete helmet.

BACKGROUND ART

In general, a helmet is used to protect a user's head. Such a helmet is widely being used so as to protect the head of a human body, the use purpose of which may be categorized into a construction and industry purpose for the use at various construction and labor sites, a leisure sports industry purpose for a bicycle, an auto-bike, an inline skate, etc., and a disaster-associated industry purpose, for example, in the field of an earthquake, a disaster, etc.

As illustrated in FIG. 1, the helmet 2 in the conventional technology in general is made of a metallic material or a plastic material, which results in a big size and a heavy weight, for which it is not east to carry. For this reason, the users in general hate wearing such a helmet.

Since the user does not carry the helmet, the user inevitably works not wearing the helmet. In this case, it is impossible to substantially protect the user's head at the work site, thus causing a problem, for example, a big manmade accident.

According to the conventional technology, in order to provide an easier carrying function, a new helmet having an improved portability to carry the helmet with the aid of air injection, etc. has been developed. If the air deflates after the helmet is poked by a sharp thing in a complicated environment, for example, at a construction site, etc., the worker's head may not be effectively protected, and the manufacturing cost will increase for the above reason.

DISCLOSURE OF INVENTION

Accordingly, the present invention is made in an effort to resolve the above mentioned problems. It is an object of the present invention to provide a foldable helmet wherein the size of the helmet can be greatly reduced by folding the helmet when not in use, which provides an easier carrying and storage, and the user can unfold and wear the helmet into a complete helmet when in use, so the user's head can be substantially protected in a dangerous environment.

TECHNICAL SOLUTION

To achieve the above objects, there is provided a foldable helmet, which may include, but is not limited to, a plurality of helmet fragment which are connected rotatable to a common shaft, and the helmet fragment parts can be unfolded into a cap shape when they are unfolded in a step type into the foldable helmet; and a slide type connection means which is configured to connect a plurality of the helmet fragment parts to move slidable in the circumferential directions along the inner circumferential surfaces of the helmet fragment parts grouped in one and along the outer circumferential surfaces of the neighboring helmet fragment parts at the inner portions thereof while stably maintaining a shape at the time of the unfolding while providing an easier unfolding operation.

Preferably, the slide type connection means includes female slide parts formed in the circumferential direction on the inner circumferential surfaces of the helmet fragment parts grouped in one, and male slide parts configured to be inserted into the female slide parts on the outer circumferential surfaces of the neighboring helmet fragment parts at the inner sides thereof.

Preferably, in order to limit the rotations of a plurality of the helmet fragment parts, the helmet fragment parts grouped in one include stoppers formed to block at least one end among both ends of the female slide parts on the inner circumferential surfaces.

More preferably, in order to block the input of rain water by blocking the gap among a plurality of the unfolded helmet fragment parts, the helmet fragment parts grouped in one include rain water input prevention protrusion parts formed at a portion where the helmet fragment parts are formed overlapping, while protruding in the meridian direction from the inner circumferential surfaces.

More preferably, for the rain water input prevention protrusion parts to be inserted at a portion where the helmet fragment parts are being overlapped, the neighboring helmet fragment parts at the inner portions thereof include rain water input prevention groove parts formed in the shapes of grooves in the meridian directions on the outer circumferential.

More preferably, there is further provided a connection tightening means configured to connect a plurality of the helmet fragment parts to a common shaft in a tightening method in order for the rain input prevention protrusion parts and the rain input prevention groove parts to be firmly engaged as a plurality of the unfolded helmet fragment parts are contacting close to one another.

More preferably, the first helmet fragment part includes first engaging part 18 formed protruding from the inner circumferential surface at a portion where the first helmet fragment part and the last helmet fragment part are overlapping for a plurality of the unfolded helmet fragment parts to maintain a cap shape, and the last helmet fragment part includes a second engaging part formed protruding to be hooked by the first engaging part on the outer circumferential surface.

More preferably, head strap attachment and detachment parts provided for heat strap to be attached or detached are dispose on the inner circumferential surfaces of the helmet fragment and on the common shaft at the inner portions of a plurality of the unfolded helmet fragment parts.

ADVANTAGEOUS EFFECTS

According to the foldable helmet of the present invention, a plurality of helmet fragment parts can be easily unfolded and folded. When not in use, the user is able to fold the helmet fragment parts in a slide way, thus greatly reducing the size of the helmet, which results in an easier carrying and storage. When in use, the helmet can be unfolded into a complete helmet, and the user can wear the complete helmet, so it is possible to substantially protect the user's head in a dangerous environment.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a conventional helmet.

FIGS. 2, 3A and 3B are perspective, plane and bottom views illustrating an unfolded state of a foldable helmet according to the present invention.

FIG. 4 is a perspective view illustrating a folded state of a foldable helmet according to the present invention.

FIGS. 5A and 5B are side and rear views illustrating a first helmet fragment part of a foldable helmet according to the present invention.

FIGS. 6A, 6B and 6C are plane, front and rear views illustrating a second helmet fragment part of a foldable helmet according to the present invention.

FIGS. 7A and 7B are front and rear views illustrating a third helmet fragment part of a foldable helmet according to the present invention.

FIGS. 8A, 8B and 8C are plane, front and rear views illustrating a fourth helmet fragment part of a foldable helmet according to the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

The foldable helmet according to the present invention will be described in detail with reference to the accompanying drawings.

FIGS. 2, 3A and 3B illustrate the unfolded state of the foldable helmet 1 according to the present invention, and FIG. 4 illustrates a folded state of the foldable helmet according to the present invention, and FIGS. 5 to 8 illustrate a first helmet fragment part 100, a second helmet fragment part 200, a third helmet fragment part 300, and a fourth helmet fragment part 400, which all constitute the foldable helmet of the present invention.

The foldable helmet 1 according to the present invention may include, but is not limited to, a plurality of helmet fragment parts 100, 200, 300 and 400 which are connected rotatable to a common shaft and may form a helmet shape when they are unfolded in a step type.

The foldable helmet 1 is formed in almost a hemispherical shape, and the helmet fragment parts 100, 200, 300 and 400 are configured in the shapes which are almost similar to the portions partitioned by the lines connected from the ceiling of the hemisphere to the equator line along the meridian direction.

Namely, the helmet fragment parts 100, 200, 300 and 400 may look like a divided circle when viewing them from the tops thereof, and the cross sections based on the meridian direction look line an arc shaped curve. As illustrated in the drawing, the present invention provides four helmet fragment parts 100, 200, 300 and 400, each of which is formed accounting for ¼ of the hemisphere.

The number and relative sizes of such helmet fragment parts are not limited to the disclosed configurations. It is obvious that they may be configured different as compared to the disclosed configuration, if necessary. For example, in case of the sports helmet, for example, for the users of a bicycle, an auto-bike, etc., two helmet fragment parts may be provided, which are formed by dividing the hemisphere into two. In this way, the present invention may include various modifications to the helmet fragment parts.

The helmet fragment parts 100, 200, 300 and 400 may be formed in such a way that the helmet fragment parts disposed closer to the center of the hemisphere have smaller radiuses so that they can be folded stacked layer by layer when folding them. The helmet fragment parts 100, 20, 300 and 400 may be connected to each other by a hinge method or a bolt method so that they can be rotatable about the common shaft passing through the ceiling of the hemisphere.

At this time, it is preferred that the helmet fragment parts 100, 200, 300 and 400 are made of a reinforced plastic material or a metallic material which are light and have high strengths. In addition, a special material film (not illustrated) may be additionally attached to at least one of the inner circumferential surfaces 110, 210, 310 and 410 and outer circumferential surfaces 120, 220, 320 and 420 of each helmet fragment page. For example, in case of the helmet for a military supply and defense purpose, a bulletproof material film may be attached to an outer circumferential surface of each helmet fragment part so as to protect the head from bullets.

More specifically, as illustrated in FIG. 4, when not in use, the foldable helmet 1 according to the present invention is present folded. More specifically, in the unfolded state as illustrated in FIG. 2, the fourth, third and second helmet fragment parts 400, 300 and 20 are rotated about the common shaft in order for them to position just below the third, second and first helmet fragment parts 300, 200 and 100, thus obtaining the folded state. In this case, the helmet fragment parts are arranged in such a way that the first, second, third and fourth helmet fragment parts 100, 200, 300 and 400 are stacked from the outer side to the inner side.

Meanwhile, when in use as illustrated in FIG. 2, the foldable helmet 1 according to the present invention is present unfolded. More specifically, in the folded state as illustrated in FIG. 4, the fourth, third and second helmet fragment parts 400, 300 and 200 are rotated about the common shaft so that they can separate from the third, second and first helmet fragment parts 300, 200 and 100, thus obtaining the unfolded state. At this time, the helmet fragment parts will make a complete helmet type since the first, second, third and fourth helmet fragment parts 100, 200, 300 and 400 are unfolded in the step type.

In the foldable helmet 1 according to the present invention, the counterclockwise direction when viewing in FIG. 3A represents the unfolding directions of the helmet fragment parts 100, 200 and 300, and on the contrary, the clockwise direction represents the folding direction.

According to the foldable helmet 1 according to the present invention, when in use, the helmet fragment parts 100, 200, 300 and 400 are unfolded into a complete helmet shape, thus providing a worker's safety at a work site, etc., and when not in use, the helmet fragment parts are folded, and the size of the helmet is reduced into ¼ of the hemisphere, so the size of the foldable helmet of the present invention can be greatly reduced as compared to the conventional helmet, whereupon the foldable helmet of the present invention is easy to carry and be stored.

In addition, in the foldable helmet 1 according to the present invention, each of the helmet fragment parts may include a slide type connection unit to connect the inner circumferential surfaces 110, 210 and 310 of the helmet fragment parts 100, 200 and 300, which are grouped in one, with the outer circumferential surfaces 220, 320 and 420 of the helmet fragment parts 200, 300 and 400 which are neighboring each other at the inner portions thereof in order for them to slide along the circumferential direction.

The helmet fragment parts 100, 200 and 300 grouped in one and the helmet fragment parts 200, 300 and 400 disposed close thereto at the inner portions thereof may represent a pair of the helmet fragment parts which are neighboring each other. One helmet fragment part may position at a relatively outer portion with respect the helmet fragment part which is neighboring at the inner portion thereof.

More specifically, the inner circumferential surface 110 of the first helmet fragment part 100 and the outer circumferential surface 220 of the second helmet fragment part 200, the inner circumferential surface 210 of the second helmet fragment part and the outer circumferential surface 320 of the third helmet fragment part 300, the inner circumferential surface 310 of the third helmet fragment part and the outer circumferential surface 420 of the fourth helmet fragment part 400 are respectively connected to each other in the slidable way.

For this reason, a plurality of the helmet fragment parts 100, 200, 300 and 400 can be easily unfolded and are able to maintain their shapes stable during the unfolding. Since an external impact can be transferred via a slide type connection member, not directly transferred from the helmet to the user's head, thus cushioning such an external impact.

More specifically, the slide type connection member may include female slide units 112, 212 and 312 and male slide units 222, 322 and 422.

The female slide parts 112, 212 and 312 are formed in the circumferential directions on the inner circumferential surfaces 110, 210 and 310 of the helmet fragment parts 100, 200 and 300 grouped in one, and the male slide parts 222, 322 and 422 are formed inserted in the female slide parts on the outer circumferential surfaces 220, 320 and 420 of the helmet fragment parts 200, 300 and 400 which are formed closer inward.

In case of the present invention, as illustrated in the drawings, the rail-type female slide parts 112, 212 and 312 may be formed in the circumferential directions at the lower portions of the inner circumferential surfaces 110, 210 and 310 of the first, second and third helmet fragment parts 100, 200 and 300. More specifically, the rail type female slide parts 112, 212 and 312 may have the

-shaped or

-shaped grooves on the horizontal cross sections with respect to the longitudinal directions.

The bolt type or button type male slide parts 222, 322 and 422 may be formed at the lower portions of the outer circumferential surfaces 220, 320 and 420 of the second, third and fourth helmet fragment parts 200, 300 and 400. More specifically, the bolt type or button type male slide parts 222, 322 and 422 are disposed close to the rear ends with respect to the rotation direction unfolded from the outer circumferential surfaces 220, 320 and 420 in consideration of the slide displacements. In addition, the male slide parts 222, 322 and 422 are formed of connection parts connecting the heads to the outer circumferential surfaces. Here, the

-shaped or

-shaped portions are inserted in the

-shaped or

-shaped portions of the female slide parts 112, 212 and 312.

Since the bolt type or button type male slide parts 222, 322 and 422 are inserted in the rail type female slide parts 112, 212 and 312 and slide along the rails, the helmet fragment parts 200, 300 and 400 disposed close to the inner portion of the helmet fragment parts mentioned below can be stably unfolded and folded with respect to the helmet fragment parts 100, 200 and 300 grouped in one.

Not illustrated in the drawing, the female slide parts and the male slide parts may be disposed with their positions being switched. The male slide parts are not limited to the illustrated bolts or button types, for example, they may be configured in the rail types which can be inserted in the female slide parts.

Preferably, in order to limit the rotations of a plurality of the helmet fragment parts 100, 200 and 300, the helmet fragment parts 100, 200 and 300 grouped in one may include stopper parts 114, 214 and 314 which are able to block any one end among both ends of the female slide parts 112, 212 and 312 on the inner circumferential surfaces 110, 210 and 310.

More specifically, referring to the drawings, the first, second and third helmet fragment parts 100, 200 and 300 may include stopper parts 114, 114′ 214 and 314 which formed protruding to block both ends of the female slide parts 11, 212 and 312 on the inner circumferential surfaces 110, 210 and 310.

When the second, third and fourth helmet fragment parts 200, 300 and 300 positioning at the relatively inner portions rotate at the inner portions of the first, second and third helmet fragment parts 100, 200 and 300 positioning at the relatively outer portions, the helmet fragment parts at the inner portions are blocked by the stoppers 114, 114′ 214 and 314 of the helmet fragment parts at the outer portions, whereupon they could not separate from the helmet fragment parts positioning at the outer portions.

More preferably, the stopper part 114′ formed at the rear end portion with respect to the unfolding direction among the stoppers 114 and 114′ of the first helmet fragment part 100 may have a predetermined height which is over the thicknesses of all the three helmet fragment parts so as to limit the rotations of all the second, third and fourth helmet fragment parts 200, 300 and 400.

If a plurality of the helmet fragment parts 200, 300 and 400 rotate in one direction during the unfolding, they can be unfolded into a complete helmet 1. If they rotate in the opposite direction during the unfolding, they may not be unfolded into a complete helmet. The stopper part 114′ of the first helmet fragment part 100 will interrupt the rotation in the opposite direction of a plurality of the helmet fragment parts, thus guiding them to rotate only in one direction and unfold.

In addition to this, for the sake of the assembling and disassembling of a plurality of the helmet fragment parts 100, 200, 300 and 400, there may be provided opening parts 115, 215 and 315 which are suitable to engage the male slide parts 222, 322 and 422 to the female slide parts 112, 212 and 312 and to discharge them.

More specifically, as illustrated in the drawings, the female slide parts 112, 212 and 312 may include openings 115, 215 and 315 which are formed larger than the heads so that the heads of the male slide parts 222, 322 and 422 can be inserted from the rear end portions with respect the unfolding direction.

Next, the helmet fragment parts positioning at the relatively outer portions may include rain water input prevention protrusion parts 116, 216 and 316 which are formed protruding in the meridian direction from the inner circumferential surfaces at the portion where the helmet fragment parts are being overlapped.

Even in case where the helmet fragment parts 100, 200, 300 and 400 are unfolded into a complete helmet 1, a gap may be inevitably formed between the helmet fragments due to their innate structures. For this reason, the rain water may input during the use of the helmet.

To resolve the above problems, the present invention may provide rain water input prevention protrusion parts 116, 216 and 316, thus preventing the inputs of rain water by blocking the gaps between a plurality of the helmet fragment parts 100, 200, 300 and 400.

More specifically, as illustrated in the drawings, the first, second and third helmet fragment parts 100, 200 and 300 may protrude long along the meridian direction or the vertical direction from the front end portions in the unfolding directions of the helmet fragment parts among the inner circumferential surfaces 110, 210 and 310. At this time, the end portions represent the ends and the portions formed near the ends and may be used as the same meaning on the whole.

When the second, third and fourth helmet fragment parts 200, 300 and 400 are unfolded with respect to the first, second and third helmet fragment parts 100, 200 and 300, the rain water input prevention protrusion parts 116, 216 and 316 of the first, second and third helmet fragment parts will contact close with the outer circumferential surfaces 220, 320 and 420 of the second, third and fourth helmet fragment parts, thus removing most of the gaps between the helmet fragment parts.

As described above, the helmet fragment parts 100, 200, 300 and 400 have the radiuses which become smaller in the direction of the center of the hemisphere, so gaps may be formed between the first helmet fragment part 100 and the fourth helmet fragment part 400 in a state where the helmet fragment are unfolded.

In order to remove the above gaps, the first helmet fragment part 100 may has a portion which extends inward from the portion where it overlaps with the fourth helmet fragment part 400.

More specifically, as illustrated in the drawings, the first helmet fragment part 100 may have an extension part 117 which is protruding in the meridian direction from the whole rear end portions with respect to the unfolding direction.

Meanwhile, the thusly formed extension part 117 may be formed at the same portion as the stopper part 114′ of the first helmet fragment part 100. In addition, the extension part 117 itself may become the rain water input prevention protrusion part or may have a component which has the same function as the same.

Preferably, the helmet fragment parts 200, 300 and 400 positioning nearer inward with respect to the helmet fragment parts 100, 200 and 300 grouped in one may have rain water input prevention groove parts 226, 326 and 426 formed in the groove shapes in the meridian directions on the outer circumferential surfaces at the portion where the helmet fragment parts are overlapping.

At this time, the rain water input prevention groove parts 226, 326 and 426 are configured correspondingly inserted in the rain water input prevention protrusion parts 116, 216 and 316.

More specifically, as illustrated in the drawings, the second, third and fourth helmet fragment parts 200, 300 and 400 may be formed in the long groove shapes formed in the meridian direction or the vertical direction at the rear end portions with respect to the unfolding directions of the helmet fragment parts among the outer circumferential surfaces 220, 230 and 240.

When the second, third and fourth helmet fragment parts 200, 300 and 400 are unfolded with respect to the first, second and third helmet fragment parts 100, 200 and 300, the rain water input prevention protrusion parts 116, 216 and 316 of the first, second and third helmet fragment parts are engaged to the rain water input prevention groove parts 226, 326 and 426 of the second, third and fourth helmet fragment parts, it is possible to reliably prevent the rain water from entering via the helmet fragment parts.

At the same time, since the rain water input prevention protrusion parts 116, 216 and 316 and the rain water input prevention groove parts 226, 326 and 426 are engaged, it is possible to prevent the neighboring helmet fragment parts from over rotating and separating from each other. Namely, the unfolded helmet fragment parts 100, 200, 300 and 400 are able to firmly keep a complete helmet shape with the aid of the above engaging function.

Meanwhile, not specifically illustrated in the drawings, a rain water input prevention groove part to which the extension part 117 of the first helmet fragment part 100 or the rain water input prevention protrusion part formed thereon is engaged may be additionally formed on the outer circumferential surface 420 of the fourth helmet fragment part 400.

Not illustrated in the drawings, if the rain input prevention protrusion part is used alone without the rain water input prevention groove part, the rain input prevention protrusion part may position at the rain water input prevention groove part. In the same way, if the rain water prevention protrusion part and the grove part are employed together, the positions thereof may be switched. It is obvious that such simple modifications are also included in the scope of the present invention.

More preferably, the foldable helmet 1 according to the present invention may include a connection tightening unit 500 which is able to connect in a tightening way at the common shaft a plurality of the helmet fragment parts 100, 200, 300 and 400. For example, not illustrated in the drawings, the connection tightening unit may be formed in a bolt type.

The complete helmet 1 is made by unfolding the helmet fragment parts 100, 200, 300 and 400, and then the connection tightening unit 500 tighten them, whereupon a plurality of the unfolded helmet fragment parts will contact close each other, so the rain water input prevention protrusion parts 116, 216 and 316 and the rain water input prevention groove parts 226, 326 and 426 can be more firmly engaged.

So, the rain water input prevention effect between the helmet fragment parts 100, 200, 300 and 400 can be more enhanced, and the stability and durability of the helmet shapes can be more enhanced.

The connection tightening unit 500 may be more effective if it is used together with the rain input prevention protrusion parts 116, 216 and 316 and the groove parts 226, 326 and 426. An occasion where it is formed in a single form is not excluded. Even if it is used in a single form, a desired effect may be substantially obtained.

Next, at a portion where the first helmet fragment part 100 and the last helmet fragment part 400 are overlapping, the first helmet fragment part may include a first engaging part 118 which is protruding from the inner circumferential surface 110. The last helmet fragment part may include a second engaging part 426 which is protruding and is hooked by the first engaging part on the outer circumferential surface 420.

Since the first engaging part 118 and the second engaging part 428 are engaged with each other in a state where a plurality of the helmet fragment parts 100, 200, 300 and 400 are unfolded, it is possible to firmly maintain a complete helmet shape.

More specifically, the first helmet fragment part 100 which is the first helmet fragment part in the present invention may include a first engaging part 118 which is formed protruding in the meridian direction or the vertical direction from the rear end portion with respect to the unfolding direction.

The fourth helmet fragment part 400 which is the last helmet fragment part may include a second engaging part 428 which is formed protruding to correspond to the first engaging part 118 in the meridian direction or the vertical direction at the rear end portion in the unfolding direction on the outer circumferential surface 420.

As described above, the radiuses are decreasing from the first helmet fragment part 100 to the fourth helmet fragment part 400, a gap may be formed between the first helmet fragment part and the fourth helmet fragment part after the helmet fragment parts 100, 20, 300 and 400 are unfolded.

It therefore is preferred that the first engaging part 118 is formed at the extension part 117 wherein the rear end portion with respect to the unfolding direction on the inner circumferential surface 110 of the first helmet fragment part 100 is extending inward of the hemisphere for the sake of an engagement with the second engaging part 428.

Next, the foldable helmet 1 according to the present invention may include inner circumferential surfaces 110, 210, 310 and 410 formed at the inner portions of a plurality of the unfolded helmet fragment parts 100, 200, 300 and 400, and head strap attachment and detachment parts 130, 230, 330, 430 and 530 which are configured for the head straps to be detachably attached to the portion of the common shaft.

The foldable helmet 1 according to the present invention may form the exterior of the helmet. The head strap is engaged to the inside thereof for the sake of the mounting on the user's head.

For this, one or more head strap attachment and detachment part 130, 230, 330 and 430 may be provided at the lower portions of the inner circumferential surfaces 110, 10, 310 and 410 of the helmet fragment parts 100, 200, 300 and 400, more specifically, on the tops of the female slide parts 112, 212 and 312. The above head strap attachment and detachment parts 130, 230, 330 and 430 may be provided in the bolt or button types, and the head strap is fixed hooked by the head portion of the head strap attachment and detachment part.

In more detail, as illustrated in the drawings, it is preferred that the head strap attachment and detachment parts 130, 230 and 330 are engaged at the heat strap attachment and detachment groove parts 132, 232 and 32 formed on the inner circumferential surfaces 110, 210 and 310 for the helmet fragment parts 200, 300 and 400 at the inner portions to slide inward of the helmet fragment parts 120, 230 and 330 at the outer portions. More preferably, the head strap attachment and detachment parts 130, 230 and 330 of the first, second and third helmet fragment parts 100, 200 and 300 are formed not protruding from the inner circumferential surfaces 110, 210 and 310.

Meanwhile, the head strap attachment and detachment part 430 of the fourth helmet fragment part 400 does not interfere with the slide folding of a plurality of the helmet fragment parts 100, 200, 300 and 400, they can be formed protruding.

Moreover, a head strap attachment and detachment part 530 may be further provided at a portion of the common shaft so as to detachably fix the top of the heat strap. This head strap attachment and detachment part 53, as illustrated in the drawings, may be formed in a

-shape one side of which is open. So, the head strap can be engaged or separated via the open portion.

The foldable helmet 1 according to the present invention may include a portable ring part 140 formed at a portion of the common shaft of the first helmet fragment part 100 for the sake of easier carrying. As illustrated therein, the first helmet fragment part 100 may include the portable ring part 140 which is formed in a ring shape at a portion of the common shaft.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. 

1. A foldable helmet, comprising: a plurality of helmet fragment parts which are connected rotatable to a common shaft, wherein the plurality of helmet fragment parts can be unfolded into a cap shape when being unfolded in a step type into the foldable helmet; and a slide type connection means which is configured to connect the plurality of helmet fragment parts to move slidable in the circumferential directions along inner circumferential surfaces of the plurality of helmet fragment parts grouped in one and along outer circumferential surfaces of the plurality of neighboring helmet fragment parts at inner portions thereof while stably maintaining a shape at the time of the unfolding while providing an easier unfolding operation.
 2. The helmet of claim 1, wherein the slide type connection means includes female slide parts formed in the circumferential direction on the inner circumferential surfaces and male slide parts configured to be inserted into the female slide parts on the outer circumferential surfaces.
 3. The helmet of claim 2, wherein in order to limit the rotations of the plurality of helmet fragment parts, the plurality of helmet fragment parts grouped in one include stoppers formed to block at least one end among both ends of the female slide parts.
 4. The helmet of claim 1, wherein in order to block the input of rain water by blocking the gap among the plurality of the unfolded helmet fragment parts, the plurality of helmet fragment parts grouped in one include rain water input prevention protrusion parts formed at a portion where the plurality of helmet fragment parts are formed overlapping, while protruding in the meridian direction from the inner circumferential surfaces.
 5. The helmet of claim 4, wherein for the rain water input prevention protrusion parts to be inserted at a portion where the helmet fragment parts are being overlapped, the plurality of neighboring helmet fragment parts at the inner portions thereof include rain water input prevention groove parts formed in the shapes of grooves in the meridian directions on the outer circumferential surfaces.
 6. The helmet of claim 5, further comprising a connection tightening means configured to connect the plurality of helmet fragment parts to a common shaft in a tightening method in order for the rain input prevention protrusion parts and the rain input prevention groove parts to be firmly engaged as the plurality of unfolded helmet fragment parts are contacting close to one another.
 7. The helmet of claim 1, wherein a first helmet fragment part includes a first engaging part formed protruding from the inner circumferential surface at a portion where the first helmet fragment part and the last helmet fragment part are overlapping for the plurality of unfolded helmet fragment parts to maintain a cap shape, and the last helmet fragment part includes a second engaging part formed protruding to be hooked by the first engaging part on the outer circumferential surface.
 8. The helmet of claim 1, wherein head strap attachment and detachment parts provided for a heat strap to be attached or detached are disposed on the inner circumferential surfaces and on the common shaft at the inner portions of the plurality of unfolded helmet fragment parts.
 9. The helmet of claim 3, wherein in order to block the input of rain water by blocking the gap among the plurality of the unfolded helmet fragment parts, the plurality of helmet fragment parts grouped in one include rain water input prevention protrusion parts formed at a portion where the plurality of helmet fragment parts are formed overlapping, while protruding in the meridian direction from the inner circumferential surfaces.
 10. The helmet of claim 9, wherein for the rain water input prevention protrusion parts to be inserted at a portion where the helmet fragment parts are being overlapped, the plurality of neighboring helmet fragment parts at the inner portions thereof include rain water input prevention groove parts formed in the shapes of grooves in the meridian directions on the outer circumferential surfaces.
 11. The helmet of claim 10, further comprising a connection tightening means configured to connect the plurality of helmet fragment parts to a common shaft in a tightening method in order for the rain input prevention protrusion parts and the rain input prevention groove parts to be firmly engaged as the plurality of unfolded helmet fragment parts are contacting close to one another.
 12. The helmet of claim 2, wherein in order to block the input of rain water by blocking the gap among the plurality of the unfolded helmet fragment parts, the plurality of helmet fragment parts grouped in one include rain water input prevention protrusion parts formed at a portion where the plurality of helmet fragment parts are formed overlapping, while protruding in the meridian direction from the inner circumferential surfaces.
 13. The helmet of claim 12, wherein for the rain water input prevention protrusion parts to be inserted at a portion where the helmet fragment parts are being overlapped, the plurality of neighboring helmet fragment parts at the inner portions thereof include rain water input prevention groove parts formed in the shapes of grooves in the meridian directions on the outer circumferential surfaces.
 14. The helmet of claim 13, further comprising a connection tightening means configured to connect the plurality of helmet fragment parts to a common shaft in a tightening method in order for the rain input prevention protrusion parts and the rain input prevention groove parts to be firmly engaged as the plurality of unfolded helmet fragment parts are contacting close to one another. 